Delay expression jack for Feedback

[Luke51411]

I'm thinking of adding an expression jack for the feedback pot of a delay but instead of using a typical expression pedal I want to just do a momentary switch that ramps up the brightness of an LED that drives an LDR. I'm thinking of hacking the detune part of the multiplex circuit for the expression pedal and probably adding pots for ramp up and down speed and maybe depth. Is there any reason this wouldn't work? I know, I'll probably have to experiment but I don't have the delay together yet so I'm just curious if anyone has tried something similar.